1. Field of the Invention
The present invention relates to a method for manufacturing a piezoelectric oscillator for use in electronic apparatuses such as portable communication units.
2. Description of the Related Art
Electronic apparatuses such as portable communication units have conventionally employed piezoelectric oscillators such as a temperature-compensated quartz-crystal oscillator.
As such a conventional piezoelectric oscillator, there is known one shown in FIG. 26 and FIG. 27, for example. The oscillator includes a substrate 21 having a plurality of external terminals 22 on a lower side thereof and a recess 25 on an upper side thereof, and is constructed such that a quartz-crystal oscillator device 24 and an IC 26 for controlling an oscillation output of the quartz-crystal oscillator device 24 are accommodated in the recess 25, and that an aperture of the recess 25 is hermetically sealed with a closure 27.
The substrate 21 of such a piezoelectric oscillator 21 is normally formed using a “batch processing” method wherein a large substrate formed from a ceramic material such as alumina ceramics is divided into pieces so as to obtain plural substrates 21 at a time. The IC 26 and the quartz-crystal oscillator device 24 are sequentially mounted/accommodated in the respective recesses 25 of the individual substrates 21 thus obtained by dividing the large substrate. Subsequently, the closure 27 is fixed to the respective recesses 25 on the upper sides of the substrates 21 by seam welding or the like conventionally known in the art in a manner to close the respective apertures of the recesses 25. In this manner, the conventional piezoelectric oscillators are manufactured.
The IC 26 incorporates therein a temperature compensating circuit for compensating for the oscillation output of the piezoelectric oscillator based on temperature compensation data generated based on temperature characteristics of the quartz-crystal oscillator device 24. Hence, a write control terminal 28 for inputting the temperature compensation data is provided on a lateral side or the like of the substrate 21 such as to allow the aforesaid temperature compensation data to be stored in a memory in the IC 26 after the assembly of the piezoelectric oscillator.
Unfortunately, the conventional manufacturing method as described above has the following problem. According to this method, after the large ceramic substrate is divided into pieces (substrates 21), the quartz-crystal oscillator device 24 and the IC 26 are mounted in the respective recesses 25 of the substrates 21 and then, the closure 27 is assembled to the respective substrates. In this case, the mounting operations of the quartz-crystal oscillator device 24 and of the IC 26 and the operation of assembling the closure 27 require each substrate 21 to be positively fixed as retained by a carrier in order to ensure that the quartz-crystal oscillator device 24 and the IC 26 are precisely mounted on the substrate and that the closure 27 is precisely assembled to the substrate.
Therefore, the conventional manufacturing method as described above requires additional facilities for manufacturing the carrier and the like for fixedly retaining the substrate 21, and also a cumbersome step of loading the substrate on the carrier. This leads to a drawback of lowering the productivity of the piezoelectric oscillator.
Furthermore, the conventional piezoelectric oscillator is provided with the write control terminal 28 at the lateral side or the like of the substrate 21 such as to allow for the input of the temperature compensation data. This dictates the need to provide a space for the write control terminal 28 on the surface of the substrate 2. Thus, the substrate 21 is accordingly increased in the area with respect to the face thereof or the thickness thereof, thus constituting an obstacle to the size reduction of the whole structure of the oscillator. Where the write control terminal 28 is disposed on the lateral side of the substrate 21, complicated processes must be done, which include: forming through-holes in the large ceramic substrate used for manufacturing the substrates 21; depositing an electrode pattern on an inside surface of each through-hole; and such. This results in a lowered productivity.
On the other hand, the mounting of the piezoelectric oscillator on an external circuit board involves fear that some of a conductive bonding material used for bonding the piezoelectric oscillator to the external circuit board may be adhered to the write control terminal 28, causing the piezoelectric oscillator to short with the external terminal. This leads to a drawback of cumbersome handling of the product.
In addition, the following problem also exists. Since it is difficult to perform the writing operation with a probe of a write device held in contact with the write control terminal 28 on the lateral side of the substrate, the following procedure is taken. That is, a socket dedicated to the writing of the temperature compensation data is prepared. Each piezoelectric oscillator need be mounted to the socket so as to permit the writing of the temperature compensation data. This requires not only additional facilities for manufacturing the socket and the like, but also a cumbersome step of mounting each piezoelectric oscillator to the socket. As a result, the manufacturing process is complicated.
It is an object of the invention to provide a method for manufacturing a piezoelectric oscillator which provides a compact piezoelectric oscillator featuring easy handling and high productivity.